Need Help Wiring Honeywell Lyric T5 to Trane 4WCX Heat Pump

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Old 12-08-17, 11:04 AM
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Need Help Wiring Honeywell Lyric T5 to Trane 4WCX Heat Pump

Hello:

I am trying to set up a new Honeywell Lyric T5 WiFi thermostat to replace an old Honeywell Focus Pro. I've read through these forums and found posts from people with similar but not identical challenges and am hoping for some assistance. I'm not an electrical expert so bear with me.

The old thermostat was wired as follows:
Red --> R+RC
Blue --> O/B
Green --> G
Yellow --> Y

There was no common wire (C) hooked up, however there are several wires tucked behind the wall plate. They are orange, brown, black and white.

I got on my roof to try and trace the wires back to the control panel to see which one might be the C wire -- I didn't find a C terminal but I did read through the product literature for my Trane 4WCX3036 system and can see that the common wire is labeled B in these models. http://www.americancoolingandheating...ifications.pdf. I am also not certain if I am looking at the right control panel -- I will post a photo below for reference. I could not see a circuit board and I am assuming the plastic wire harness is what I should be looking at. My questions are as follows:

1. Am I looking in the right place for my Trane system or should I be looking for a different circuit board?
2. If this is the right connection point, from the photo it looks like the B (common) wire is Blue. O could be black or orange but I am not sure? Would I put one of these in the O/B slot?
3. If the B wire is not the common and is supposed to stay in O/B as it was before, which would be the common and is it already hooked up on the heat pump end?
3. Once I hook the system up properly would I program the thermostat to O/B on heat or O/B on cool?

If I can get these questions answered I think I can get the problem solved. Thank you!

Carrie W.
 
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Old 12-08-17, 11:12 AM
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Welcome to the forums.

Correct.... on a Trane.... the B is the C connection.

That is the fan timer board. C may be there but I'd rather you connected at the proper location. If you are at the air handler...... find where the thermostat cables connect. That should be where you'll find the C connection.
 
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Old 12-08-17, 11:16 AM
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Hi Pete. Thank you for the quick response. Could you give me a hint as to where I would find the thermostat wires in the roof unit? I couldn't make them out last night when I was looking. I'm attaching one more photo of what i could see.

Incidentally there are three compartments in the front of my unit -- compressor, blower and heating control.

 
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Old 12-08-17, 11:29 AM
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They will come in the same place as the AC power wiring, They should be behind that panel.
 
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Old 12-08-17, 11:36 AM
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OK I will have to take a look when I get home from work this afternoon. Will I be looking for a typical circuit board or is it likely to be a plastic connector like the one pictured?

If the blue does turn out to be the C and not the O/B as it was previously wired do you have any guidance on what to look for once I get up there for that?
 
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Old 12-08-17, 03:38 PM
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OK I think I may have found the answer. Tracing what I think are the thermostat wires it looks like black and red lead to the same point with black possibly being the common wire?? There is also one more connection point with a label that says "C" and it's hard to see from the photo but that wire is black. Please see the photos below and let me know if I am correct...I think I need to connect black to C and blue to O/B.

Thank you for your help.
 
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Old 12-08-17, 04:05 PM
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I'm trying to work thru the pictures. I do not see any thermostat wires in any of those pictures.

You are looking for a brown cable with red, blue, green yellow connected and orange, brown, black and white not connected.

The numbers and letters you see printed on those wires will be on a wiring diagram posted on the back of the wiring door you removed.

I just saw the link you posted.
36G(blue) and 38A (green) ARE a C connection and because the C connection is grounded to the metal frame.... you can connect to any screw in metal for C.

In your original wire colors..... they've used blue for the O connection. In order to keep with standards..... you should use the blue for your C and make orange the O wire.

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I'm not seeing any W connection which means no back up electric heat.
 

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Old 12-08-17, 04:39 PM
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Thank you!

Pete:

That is very helpful!! Thank you. So if I am reading you correctly I don't need to do anything on the heat pump end I should just switch the wires on the thermostat end?

Also I did take one more photo that I think *might* be thermostat wires.
Apologies for being such a green horn.
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Old 12-08-17, 04:53 PM
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Added in picture.

Move the stat blue from the heavy orange wire to the heavy blue wire.
Move the stat orange wire to the heavy orange wire.

Make orange O at the stat and make blue C.
Don't forget.... kill power to that monster when messing with the wiring,
 
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Old 12-08-17, 05:43 PM
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Great!! I'll do all of that in the morning and let you know how it goes.
 
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Old 12-09-17, 11:41 AM
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Hi Pete:

We have liftoff! If those stat wires had been a snake they would have gotten me for sure. I got everything switched up (breakers off of course) and wired the thermostat as you suggested. I'll copy an image of the redirected stat wires below.

Thank you for your help along the way -- very appreciated.

 
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